package lq;

import java.util.Scanner;

public class lq2004 {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        int sorce;
        while (in.hasNext()){
            sorce=in.nextInt();
            if (sorce<=100&sorce>=0){
                if (sorce>=90){
                    System.out.println("A");
                }
                if (sorce>=80&sorce<90){
                    System.out.println("B");
                }
                if (sorce>=70&sorce<=79){
                    System.out.println("C");
                }
                if (sorce>=60&sorce<=69){
                    System.out.println("D");
                }
                if (sorce>=0&sorce<=59){
                    System.out.println("E");
                }
            }
            else{
                System.out.println("Score is error!");
            }
        }
    }
}
